1. Field of the Invention
The present invention relates to an optical system in which various substances in a sample are analyzed while rotating the sample in a centrifugal separator, and, in particular, to an optical system in which a sample such as polysaccharide and/or glycoprotein having no light absorption property is analyzed by irradiating the sample with light.
2. Description of the Related Art
A sample containing various substances is generally set in a rotator of a centrifugal separator to optically analyze the various substances. For example, the sample contains polysaccharide and/or glycoprotein which have no light absorption property within a measuring wavelength.
In detail, because each of the various substances has its specific gravity, the various substances are separated from one another by a centrifugal force after the sample is rotated in the rotator. Thereafter, the sample is irradiated with light. In this case, because each of the various substances also has its index of refraction, the phase speed of the light penetrating a substance with a high index of refraction is smaller than that of the light penetrating another substance with a low index of refraction. Therefore, a phase difference occurs between the lights penetrating the substances. Thereafter, the phase difference is analyzed by measuring interference fringes produced by optically interfering the lights to determine the shift of the specific gravity of the sample along a radial direction of the rotator.
2.1. Previously Proposed Art
A conventional optical system for analyzing a sample by utilizing a centrifugal separator is described with reference to FIGS. 1 to 5.
FIG. 1 is a schematic view of a conventional optical system for optically analyzing samples by utilizing a centrifugal separator, and FIG. 2 is a plan view of both a test sample and a reference sample arranged in a sample cell shown in FIG. 1.
As shown in FIG. 1, a conventional optical system 11 is provided with a columnar sample rotator 12 and a plurality of sample cells 13 arranged in hollow portions of the sample rotator 12. The sample rotator 12 is accommodated in a vacuum vessel 14, and the sample cells 13 are positioned at equal distances from a rotation axis 15 of the sample rotator 12. As shown in FIG. 2, both a test sample 16 and a reference sample 17 are arranged side by side in each of the sample cells 13. The test sample 16 consists of various substances which each have both a specific gravity and an index of refraction. The reference sample 17 consists of a reference substance, and an index of refraction of the reference substance is known in advance.
The system 11 is further provided with a mercury lamp 18 for generating monochromatic light 19, an incident light window 20 arranged on a surface of the vacuum vessel 14 for transmitting the monochromatic light 19 generated by the mercury lamp 18 into the vacuum vessel 14 to irradiate the sample cells 13 with the monochromatic light 19, a pair of reflecting mirrors 21, 22 for simultaneously reflecting both a light 23a which transmits through the test sample 16 and a light 23b which transmits through the reference sample 17, a light window 24 arranged on another surface of the vacuum vessel 14 for transmitting the lights 23a, 23b reflected by the reflecting mirror 22 towards the outside of the vacuum vessel 14, and a pair of prisms 25, 26 for producing interference fringes by optically interfering the lights 23a, 23b.
The light 19 generated by the mercury lamp 18 transmits through both the test sample 16 and the reference sample 17 in the sample cell 13 without being absorbed by the samples 16, 17.
In the conventional optical system 11 having the configuration outlined above, an operation for optically analyzing the substances in the test sample 16 is described.
Various types of test samples 16 are initially arranged in the sample cells 13. Also, the sample cells 13 respectively accommodate the same reference sample 17. Thereafter, the sample rotator 12 is rotated about its rotation axis 15. In this case, because the test sample 16 consists of various substances with various specific gravities, the various substances are separated from one another by a centrifugal force generated by the rotation of the sample rotator 12. The centrifugal force acts in a radial direction Rd of the sample rotator 12. That is, substances having small specific gravities are moved towards the rotation axis 15 of the sample rotator 12, and other substances having large specific gravities are moved towards the periphery of the sample rotator 12. Therefore, as shown in FIG. 3, the specific gravity of the test sample 16 is increased from an rotation axis region of the sample rotator 12 to a periphery region. Specifically, in cases where the test sample 16 consists of two main substances, the specific gravity of the test sample 16 is suddenly increased at a middle region.
In addition, because each of the various substances of the test sample 16 has an index of refraction, the index of refraction of the test sample 16 changes along the radial direction Rd of the sample rotator 12 in the same manner as the specific gravity, as shown in FIG. 3.
On the other hand, because the reference sample 17 consists of the reference substance, the specific gravity of the reference sample 17 does not change along the radial direction Rd in the sample cell 13. Also, the index of refraction of the reference sample 17 does not change along the radial direction Rd.
Thereafter, both the test sample 16 and the reference sample 17 in one of the sample cells 13 are simultaneously irradiated from just above with the monochromatic light 19 which is generated by the mercury lamp 18 and transmits through the incident light window 20. Therefore, the phase velocity of the monochromatic light 19 is reduced in both the test sample 16 and the reference sample 17 so that a phase difference occurs between the light 23a transmitting through the test sample 16 and the light 23b transmitting through the reference sample 17. In addition, the monochromatic light 19 is not refracted by either the test sample 16 or the reference sample 17 because the samples 16, 17 are irradiated with the monochromatic light 19 from just above. Also, because the index of refraction of the test sample 16 changes in the sample cell 13 in accordance with the distribution shown in FIG. 3, the degree of the phase difference changes in accordance with the index of refraction of the test sample 16 changing along the radial direction Rd of the sample rotator 12.
Thereafter, the lights 23a, 23b reflect on the reflecting mirrors 21, 22 and transmit the prisms 25, 26 through the light window 24.
FIG. 4 shows the lights 23a, 23b refracted by the prisms 25, 26 in the conventional optical system 11 shown in FIG. 1.
As shown in FIG. 4, the light 23a transmitting through the test sample 16 is refracted by the prism 25, and the light 23b transmitting through the reference sample 17 is refracted by the prism 26. Thereafter, the shifted lights 23a, 23b refracted by the prisms 25, 26 are projected on a screen 27 to show interference fringes.
FIG. 5 shows the interference fringes projected on the screen 27, the interference fringes extending in the radial direction Rd of the sample rotator 12 being shown.
As shown in Fig. 5, the interference fringes consist of curved lines arranged at equal distances from each other and extending in the radial direction Rd. In contrast, the interference fringes would otherwise consist of straight lines arranged at equal distances from each other in cases where the various substances in the test sample 16 is not separated.
Thereafter, the interference fringes projected on the screen 27 is taken a photograph by a camera to analyze the phase distribution of the light 23a transmitting through the test sample 16 by utilizing the interference fringes.
Therefore, the distribution of the index of refraction of the test sample 16 can be relatively measured on the basis of the uniform distribution of the index of refraction of the reference sample 17. In addition, the distribution of the specific gravity of the test sample 16 can be relatively measured so that the various substances contained in the test sample 16 can be specified.
However, because the interference fringes projected on the screen 27 must be taken a photograph, it takes a lot of time to analyze the phase distribution of the light 23a transmitting through the test sample 16 by utilizing the interference fringes. Therefore, it is impossible to efficiently specify the substances contained in many test samples 16.
In addition, because an operator must take reading the interference fringes taken by a photograph with the eye, the accuracy to measure the interference fringes is limited to a scale of one-tenth of the spacing between the interference fringes. Therefore, it is impossible to accurately specify the various substances contained in the test sample 16.